Thermal resistance of waffle pod slabs (July 2017)

Dr Dong Chen has investigated the Thermal Resistance of Waffle Pod Slabs – Pods with Air Cavities to identify the most appropriate method to model their performance.

Recently, the thermal resistance for waffle pod slab constructions with pod heights at 170mm, 230mm, 300mm and 370mm respectively were investigated considering air cavities in the polystyrene pods. The polystyrene pods were assumed to have a 50mm thick expanded polystyrene top and air cavities at 120mm, 180mm, 250mm and 320mm respectively. It was found that, in comparison with conventional 100mm slab-on-ground constructions, waffle pod slabs give average additional R-values of 0.57, 0.60, 0.63 and 0.65 with the 170mm, 230mm, 300mm and 370mm pod heights respectively. Based on this new research, the waffle pod slabs may be modelled by using a concrete top layer at the specified concrete thickness of the waffle pod slab system with an additional insulation layer of R0.57, R0.60, R0.63 and R0.65 for the 170mm, 230mm, 300mm and 370mm pod heights between the concrete top layer and the ground. CSIRO is currently communicating with relevant parties on potential update to the NatHERS Tech notes on this aspect.